Study On Flow Characteristics And Fluid-structure Interaction In Inclined Axis Stirred Reactor

Agitated reactor is an important equipment which makes use of the rotation of blades to make the single-phase and multi-phase materials in the reactor achieve the purpose of uniform mixing,stratified extraction,enhanced heat and mass transfer,full chemical reaction and so on.It is widely used in petrochemical industry,sewage treatment,food and medicine and other fields.Due to the comprehensive influence of many factors such as blade,kettle body,baffle,medium,speed and so on,the flow field in the kettle is complex and difficult to predict.Most domestic and foreign scholars rely on empirical formulas for the design of stirred reactors,so it is difficult to unify the standards for judging the stirring effect in the kettle.A large number of key problems need to be further studied.The research of stirred tank has practical significance and theoretical value for its standardization,large-scale,energy saving and high efficiency.In this paper,a double-layer gas-liquid two-phase stirred reactor was used as the research object,and the influence mechanism of different inclination angles of the stirring shaft on the flow field in the reactor was studied by numerical simulation.The lower layer is a self-designed propeller blade,and the upper layer is a six flat blade disk turbine blade with six circular holes.The combination of the two-layer blades is fixed,and the stirring shaft inclines every 5 ° in the range of 0 ° to 30 ° for a total of seven kinds of inclined shaft reactor models,which are designed and modeled respectively.Fluent,Workbench and MATLAB are used to calculate and process the flow field velocity under different inclination angles.In order to analyze the influence of the tilt of the stirring shaft on the flow field in the reactor,the force on the shaft and blade,the motion state of the system and the mechanism of action,the corresponding design and optimization of the stirred reactor are carried out.Through the comparative analysis of the calculation results of seven models,it is concluded that:(1)Stirring power consumption: When the inclination angle of the stirring shaft is constant,the stirring power is positively correlated with the rotational speed;when the rotational speed is constant,the stirring power is positively correlated with the inclination angle of the stirring shaft.(2)Flow distribution in autoclave: The traditional non inclined axis reactor model(0 ° inclined axis model)has obvious stirring low-speed zone at the bottom of the reactor;the velocity distribution and gas-phase diffusion effect of the reactor withα≥ 20 ° inclined axis angle are better than that of the 0 ° inclined axis reactor,and the inclination of the stirring axis significantly enhances the flow velocity of the low-speed zone at the bottom and wall of the reactor.(3)Based on the maximum Lyapunov exponent,it is concluded that when the rotation speed of 0 ° inclined axis reactor reaches 50 r/min,100 r/min and 150 r/min,the system in the reactor is in chaotic state;when the inclination angle of the stirring shaft is greater than 15 ° it is conducive to destroy the periodic movement of the flow field in the reactor,and the system in the reactor is in chaotic state;when the inclination angle of the stirring shaft is 25 ° and 30 °,the chaos degree of the system in the reactor is better than that of the 0 ° inclined axis reactor,which is conducive to medium mixing in the reactor.(4)Fluid-structure coupling analysis shows that: The results show that the maximum equivalent stress of agitator rotor(composed of agitator shaft and double-layer blades)increases with the increase of shaft inclination;the maximum static stress of 0 ° agitator rotor is distributed at the dangerous section of upper blade(near the six holes of disk),and the maximum static stress of 5-30 ° agitator rotor is distributed at the connection between shaft end and motor;when the inclination of agitator shaft reaches 30 °,the dangerous section of upper blade is located The maximum equivalent stress exceeds the allowable torsional stress of blade.Through multi angle comparison and analysis,it is concluded that the gas-liquid mixing ability of the inclined shaft stirred reactor model is better than that of the traditional non inclined shaft stirred reactor model(0 ° inclined shaft model)when the inclination angle of the stirring shaft is α≥ 20° and the 25 ° inclined shaft stirred reactor model is the best.